texlive.combine: set TEXMFCNF in binary wrapper
texlive.combine: set TEXMFCNF in binary wrapper

This helps kpathsea to find texmf.cnf in some cases. For example,
dvipng was trying to look for it in
/nix/store/<hash>-texlive-dvipng.bin-2019/ instead of
/nix/store/<hash>-texlive-combined-full-2019/.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs